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Speculative Evolution Wiki:Competitions/Comp. 2: Aquatic Supremacy/Maranulidea
Throughout the history of the earth, plenty of aquatic animals descended from terrestrial creatures have come and gone; from the plesiosaurs to the mosasaurs, and from the cetaceans to the sphenisciformes. History has a knack to repeat itself, and if the marine mammals and birds get wiped out, what primarily terrestrial clade could take the throne of aquatic adaption? This page explores one such possibility, in which Anurans, or frogs and toads, in a water-adapted juvenile state evolve neoteny, and retain their water-living features, such as gills and a powerful tail, all throughout adulthood (or put in another sense, they never reach adulthood and stay tadpoles all their lives). The amphibians had never reached such amazing diversity since their heyday in the Palaeozoic; and indeed, what amazing diversity it was. Note: this entry uses this map of future worlds: '' '' General Evolution and History This entry explores the evolution and habits of the Maranulids. But to detail their evolutionary origins, we have to go way before they evolved: to the last epoch of the Cenozoic era, the Postemary epoch. Everything seemed fine and dandy; giant mammals walked the land, giant fish and cetaceans swam the seas, and giant birds soared through the skies. However, the beginning this period, approximately 45 myf, was also the period when Africa collided with Eurasia. This set off a worldwide extinction event, causing volcanoes to erupt, vital sea currents to be disrupted and general havoc. 20% of all mammalian genera went extinct directly due to the merging, certainly devastation by any standards. But the true blight was yet to come. The collision subducted parts of the african plate below the eurasian, producing a volcanic arc of magma and toxic gases pressuring against the surface, threatening to erupt. And they did erupt; blotting out the sun, killing off plants, and filling the air with toxic. Suffice it to say, 60% of mammals went extinct, including all cetaceans, and other amniotes were similarly affected. The lower cenozoic had ended. The new cenozoic had begun. 30% of marine animals also went extinct. Mammals did rebound, and diversified once again into even more strange forms. Bird radiated as well, though by now the bats were much more of a threat to their niches. But we're not here to look at furry or feathery landlubbers. We're here to look at the amphibians and the Maranulids, which finally had their chance to evolve. The Anurans, which had hardly changed throughout the lower cenozoic, had an easier time of the Lc-Nc boundary event, as their primary prey, the insects, also did relatively well during the Lc-Nc boundary. As such, they rebounded withh great haste once the earth had sufficiently recovered. And one group which would evolve to become the Maranulids, evolved during this time. This group of stem-Maranulids, most likely descended from a species similar to the Paradoxical Frog, were wetland or marsh dwellers, and staying as a tadpole for longer was advantageous for them, due to the abundance of waterborne food, in contrast to the less common insects in the vicinity. This was the first stage in the evolution. The second stage is represented by the strange Transituherpeton of 69 myf, a highly derived, nearly fully aquatic Anuran. Transituherpeton seemingly had highly developed tadpoles that were large, nearly 30cm long, and contrastingly small and degenerate adults. The the tadpoles were the developmental stage, while the adult state existed only for reproduction. A few million years later (around 76 myf), a strange non-amphibious amphibian appeared in the fossil record. It lacked an adult stage, instead evolving the ability to reproduce as a tadpole. This creature was Marepraecursorus, and it was the first real Maranulid, a group that would soon diversify into a whole range of minute algivores, swift opportunists, and massive predators. Anatomy This applies to all Maranulids; more detail on each clade will be in the clades section. Maranulids are purely aquatic, and locomote via lateral undulation. Maranulids are descended from neotenous frogs retaining the phenotype of a tadpole, the larval form of a frog; and their anatomy reflects this, containing features of both newborn tadpoles and fully developed adult frogs. The skull of most Maranulids is relatively similar to a frog's, wedge-shaped, and split into many gracile parts. They have highly developed pedicellate teeth on the upper jaws, in which the crown is separared from the root with strong fibrous tissue; meanwhile, the lower jaw lacks teeth but often possesses projections called odontoid processes, which fill the role of teeth. Like in modern Anuran tadpoles, the rear limbs develop first, and in Maranulids they act as stabilizing fins very close to the head; the front limb remains an internalized flap. Because of the rear limb's proximity to the head, the cervical and thoracic vertebrae are few, and the lumbar vertebra only stretch back a bit behind the rear limbs. The rest are coccyxal vertebrae, and the riblike projections are actually part of the vertebra, and are not true ribs. These projections are anchor points that power the muscles for the Maranulid's lateral undulation. The tailfin is composed of a downward angled vertebral projection and an extended vertebra. Maranulids lack fully developed lungs; instead, they absorb oxygen from the water directly with gills retained from tadpoles. Water enters through the Maranulid's lungs and exits through the gills, having the oxygen absorbed out in the process. Maranulids also use the lateral line system, a mechanosensitive sense found in fish and some amphibians, to sense their surroundings. A series of hair cells cover the skin of some parts of the animal, which detect minute changes in the surrounding water, notifying the Maranulid of the state of their surroundings immediately and efficiently. Families ____________70___________________80____________________90____________________100 myf | | | | ,------------------ | ,----------/-------------------- | ----Transituherpeton---------/---------------------------- Archaeoranulidae Maranulidea